1. Field of the Invention
The present invention relates to a manipulator such as an operation-aiding manipulator or a manipulator for repairing a narrow portion of an energy device or the like. Especially, the present invention is intended to provide a power transmission mechanism using a wire and pulleys, which can be reduced in size and can be enhanced in reliability, rigidity and user-friendliness.
2. Related Background Art
In conventional laparoscope-assisted surgery such as laparoscopic cholecystectomy, a laparoscope 161, forceps 171, 172, etc. are inserted into an abdominal cavity through trocars 154 set in small incisions 151, 152, 153 made in the abdomen of a patient 150. Then, an operator (normally a surgeon) 160 conducts operation while watching the image acquired by the laparoscope on a monitor 162 as shown in FIG. 31. Since this type of operation does not need to open the abdomen, physical burden on the patient is alleviated, and the time required for recovery and discharge from the hospital after operation is greatly reduced. Therefore, its adaptation to wider fields of application is expected.
Under the background, the Inventors already proposed a medical manipulator combining a robot technique to conventional forceps (robot forceps) 1 as shown in FIG. 32 (Japanese Patent Laid-open JP-2000-350735A). This manipulator 1 includes a control command unit 20 having an attitude control unit 23 and a treatment control unit 24; a connector unit 30 having one end connected to the control command unit 20; a work unit 10 connected to the other end of the connecting unit 30 and having a treatment unit 14 and supports 15 and 16 supporting the treatment unit 14 to allow them to change in attitude in at least two degrees of freedom of motion; and a controller (not shown) for delivering a control command from the attitude control unit 23 to the supports to change the attitude of the treatment unit 14 and for delivering a control command from the treatment control unit 24 to the treatment unit 14 to activate it.
The Inventors also proposed a medical manipulator as shown in FIG. 33 as another arrangement and degrees of freedom suitable for suture and ligature (Japanese Patent Laid-open JP-2002-102248A). This medical manipulator 1 includes a work section 10, a control command unit 20, and a connector unit 30 having opposite ends connected to the work unit 10 and the control command unit 20 respectively. In the work section 10, a support unit, having a first rotation axis 11 intersecting the axial direction 31 of the connector unit 30 and a second axis 12 intersecting the first rotation axis 11, and a treatment unit (gripper) 14 for working on the target site of surgery are aligned along the second rotation axis 12. In other words, the work section 10 has a yawing-axis joint support 15 and a rolling-axis joint support 16 that function to support the gripper 14 to allow them to change in attitude in two degrees of freedom of motion. The control command unit 20 includes: an attitude control unit 23 having a third rotation axis 21 intersecting the center-axial direction 31 of the connector unit 30 and a fourth rotation axis 22 intersecting the third rotation axis 21; and a treatment control unit 24 gripped and operated by an operator whose wrist will rotate approximately in parallel to the fourth rotation axis 22. The gripping motion 13 of the treatment unit 14 for working on the target site of surgery is given by the gripping motion 25 of the treatment control unit 24.
In comparison with a remote-control master/slave manipulator, the robot forceps conjoin the control unit (master) and the forceps end hand (slave) to combine both an advantage of conventional forceps, namely enabling large and quick motions which will be effected more easily and reliably by the operator, and an advantage of a manipulator, namely, enabling minute works or controls from difficult angles. Since the robot forceps have joints for twists, rotations, and other motions, at the end, they can change the attitude of the hand freely, and make suture and ligature from various directions easier, which have been difficult with conventional forceps. The robot forceps can be used together with conventional surgical appliances, for example, by handling the robot forceps with the right hand and handling conventional forceps with the left hand. Additionally, because of the simple and compact system, the robot forceps can be introduced at a low cost.
Furthermore, manipulators having this type of configuration are suitable also for works at locations difficult for the operator to work directly at the very site, such as repair works of narrow portions of energy devices. It will be needless to say that the size (length, thickness, dimension, etc.) of the manipulator will be determined depending upon the nature of the intended work and the region of the work. Therefore, the robot forceps are not limited to the medical use.
Surgery-assisting manipulators and manipulators for repairing narrow portions in energy devices, etc. are required to be compact, lightweight, durable, easy to operate, precisely responsive to intended works and inexpensive. To meet these requirements, their power transmission mechanisms must be compact, lightweight, reliable, durable and inexpensive. Especially in the manipulators of the configurations shown in Japanese Patent Laid-open Publications JP2000-350735A and JP2002-102248A, because of the restriction by the unitary structure of the master and the slave, their shapes, sizes, arrangements of the power transmission mechanisms largely affect how they are easy to operate.
In robot and electromechanical devices and apparatuses including manipulators, power transmission for transmitting the power of an actuator to an end effector (such as a hand or tool) generally relies on wires and pulleys. In case a motion range of many revolutions is required in a power transmission mechanism using a wire and pulleys, it is usual to wind the wire 52 on pulleys 50, 51 as shown in FIG. 22 to transmit power by frictional force. To obtain a large transmission torque, a large frictional force is required. For this purpose, the wire may be wound on the pulleys over a larger angle or multiply, or the tensile force of the wire may be increased. In any of these cases, however, since the drive force basically relies on friction, a decrease of the tensile force, which may occur upon expansion of the wire, causes slips between the wire and the pulleys, and this invites a decrease of the torque. To cope with this problem, a tension adjusting mechanism is sometimes added. Therefore, it complicates the mechanism, and increases the size and the cost of the device. Furthermore, it invites a decrease of the rigidity of the joints. Furthermore, to wind the wire multiply on the pulleys, the pulleys must be wide enough to accommodate the multiple turns of the wire, and invite an increase of the device size. Usually, surgery-assisting manipulators and manipulators for repairing narrow portions of energy devices, by nature, do not have ample spaces for multiply winding a wire. On the other hand, to hold the wire on the pulleys, a fastening member 53A is usually used as shown in FIG. 23. However, in case the wire is multiply wound on the pulleys, the motion range (rotation angle) is usually limited to less than 180 degrees because of interference between the fastening member and the wire. There are some methods of increasing the winding angle as disclosed in the publication of Japanese Patent No. 2,519,749. However, the maximum angle is about 270 degrees, and it is difficult to enable rotation of 360 degrees or more. As far as the rotation range of pulleys is limited, the motion range of the manipulator joint, i.e. the work range of the end effector, remains narrow and will disturb the work by the operator. Thus, the manipulator largely degrades in fidelity to intended works and controllability. To assure an ample work region not disturbing the works, the manipulator needs the largest possible number of rotation, but this is difficult with conventional power transmission mechanisms.
On the other hand, in the power transmission mechanism using a wire and pulleys as shown in FIG. 24, in case the wire diameter is small or the drive pulley and the driven pulley are apart by a long distance, influence of elastic deformation (expansion) of the wire may increase and disable transmission of sufficient power. In addition, there is the problem that sufficient rotational rigidity is not obtained at the driven shaft (output shaft) in a hold mode where the drive pulley is stationary or in a servo lock mode. If the desired rotational rigidity is not obtained, then the manipulator degrades in controllability and fidelity to intended works, and operator cannot perform sufficient works.
In the master-slave combined manipulator conjoining the master and the slave as shown in FIGS. 25 and 27, eccentric mass about the connector unit 30 is usually produced. Depending upon the location of the eccentric mass, rotational torque out of the operator's intention may be produced by the weight about the connector unit, which degrades the controllability. Especially in the initial status at the start of controls or in the basic attitude of the manipulator, which is the most standard attitude for controls, if rotational torque is produced by eccentric mass about the connector unit, it will impose useless load to the operator and may invite significant degradation of controllability. In addition, in the manipulator having the common rolling axis, pitching axis and rolling axis as shown in FIG. 25, it is difficult to change the attitude of the work section to the yawing direction (lateral or right-and-left direction) from the basic attitude illustrated because it is the change of attitude to the singular configuration. In the arrangement of degrees of freedom shown in FIG. 29, having the illustrated common rolling axis, yawing axis, rolling axis, it is difficult to change the attitude of the work section from the illustrated basic attitude to the pitching direction (vertical or up-and-down direction) because it is the change of attitude to the singular configuration. In actual controls of the manipulator, the attitude of the work section is changed more frequently to the lateral and vertical directions from the basic attitude. Therefore, the arrangement for degrees of freedom of motion shown in FIG. 25 or 29 will invite degradation of controllability.